Assuming the car does not have stop/start system, then I would think an 027 will be correct. Dash cam and phone charger draw very little power. On most modern Peugeot models ,you cant remove the cover until the main battery positive terminal is off. There should be a quick release lever to remove it.

First step meeasure your existing battery width/height & depth in mm and note the Amp hr & CCA rating on the battery, go to a website like batterymegastore in Tewksbury and input your car details, check the dimensions of the batterys they offer and importantly the battery terminal types and positions compare to the dimensions of your own battery. If you are unsure phone them and ask, make sure you can describe accurately your battery dimensions before you phone them, A quick look tells me you can have a 096 delivered for £76,the cheapest they offer seems to me £53 the most expensive £87 ( bosch)Part Number :

Varta

• Voltage (V) : 12
• Ah : 74
• Cold Cranking : 680
• Battery Application : Engine Start inc vat £75.99
• order by 2pm for next day delivery

I've done a couple similar to this (307, Cit C4 Picasso) and it's bit of a pain. There are several different variants of the fuse box / connector on top of the battery, but it should be possible to slide it out the battery cover - although you will probably have to unbolt the +ve supply lead to get enough room to do so - and work out where the clips are. Once that is out the way the cover should come off, but it's tight, sort of needs to be pulled out and up in a rotating motion. Depending on the -ve terminal, it may be bolted on, which is a right pain - I just managed it half a flat at a time on one I did, but repositioning the clamp on re-installation meant I could get a socket on it! Hold down bolt is down the engine side, but can be got with a long extension.

I'd go for the biggest CCA you can, especially if it stands between uses and you intend to keep it. I saw a Yuassa 5000 096 on e-bay for £83 a few weeks ago - I am probably going to stick a new one in my current 3008 as it's reluctant to crank when it's been stood a few days and its cold.